The littoral zone of polar lakes: inshore–offshore contrasts in an ice-covered High Arctic lake

• Published in: Arctic Science
• Main Authors: Paschale N. Bégin, Milla Rautio, Yukiko Tanabe, Masaki Uchida, Alexander I. Culley, Warwick F. Vincent
• Format: Article in Journal/Newspaper
• Language: English; French
• Published: Canadian Science Publishing 2021
• Subjects: lake zonation; lake ice; food webs; microbial mats; underwater light; Environmental sciences; GE1-350; Environmental engineering; TA170-171; Arctic; Arctic Lake; Climate change; Zooplankton; ice covered waters
• Online Access: https://doi.org/10.1139/as-2020-0026; https://doaj.org/article/1cbf399250b549db9f8e0e48a805b17f

In ice-covered polar lakes, a narrow ice-free moat opens up in spring or early summer, and then persists at the edge of the lake until complete ice loss or refreezing. In this study, we analyzed the horizontal gradients in Ward Hunt Lake, located in the Canadian High Arctic, and addressed the hypothesis that the transition from its nearshore open-water moat to offshore ice-covered waters is marked by discontinuous shifts in limnological properties. Consistent with this hypothesis, we observed an abrupt increase in below-ice concentrations of chlorophyll a beyond the ice margin, along with a sharp decrease in temperature and light availability and pronounced changes in benthic algal pigments and fatty acids. There were higher concentrations of rotifers and lower concentrations of viruses at the ice-free sampling sites, and contrasts in zooplankton fatty acid profiles that implied a greater importance of benthic phototrophs in their inshore diet. The observed patterns underscore the structuring role of ice cover in polar lakes. These ecosystems do not conform to the traditional definitions of littoral versus pelagic zones but instead may have distinct moat, ice-margin, and ice-covered zones. This zonation is likely to weaken with ongoing climate change.